Chain saws, so that their optimal cutting performance is retained, have to be sharpened at regular intervals. In chain saws with improperly sharpened cutting teeth of the saw chains, the saw chains run erratically, the cutting performance decreases and in the worst cases, the saw chain may even tear which can in turn lead to serious accidents. The aforementioned drawbacks also lead to a high level of wear and failures of the drive machine of the chain saw.
A sharpening tool of the general type is known from DE 29 33 293 B1 (corresponding to U.S. Pat. No. 4,427,605), having a frame, which is substantially formed by two end pieces or head parts, which are connected to one another by two mutually parallel guide rods. A handle is additionally fastened to one end piece. A round file and a square file are exchangeably mounted in the end pieces or head parts. The round file is provided with a file helve which is simultaneously used as a handle of the sharpening device. Each second cutting tooth of the saw chain is filed in an arrangement of the round file and square file. To file the respective second other cutting tooth, the square file and the round file are removed from their mounting in the head parts and inserted in the opposite direction in the frame. The file helve is also removed here from one respective head part and during the changing over of the round file, inserted in the other head part and is then used as the handle of the sharpening tool. The respectively required conversion of the sharpening device is laborious.
By increasing filing off of the tooth front with the cutting face, the cutting edge changes its position perpendicular to the cutting direction, and in fact comes closer and closer to the actual saw chain, as the free face of each cutting tooth has a relief angle relative to the cutting direction, so the tooth back limited by the free face does not grind or rub on the wood to be cut. Since the guide rods rest on the free faces of two adjacent cutting teeth, the profile of the cutting face and the tooth front are displaced parallel to the free face when sharpening the cutting edge by filing the cutting face and the tooth front. The depth limiter is also filed off simultaneously, so the cutting depth, i.e. the spacing between the cutting edge and depth limiter, always remains constant perpendicular to the cutting direction.
The invention is based on the object of providing a sharpening device of the general type, which allows alternate sharpening of the respective alternating different teeth of a saw chain without conversion of the sharpening device.
This object is achieved according to the invention in a sharpening device for manually sharpening the cutting teeth of saw chains for chain saws,                with a longitudinal axis,        with a frame, which has                    a first head part and a second head part arranged at a spacing from one another and            two pairs of, in each case, two guide rods, which are arranged parallel to one another and to the longitudinal axis and rigidly connect the first and the second head part to one another,                        with in each case one round file associated with each pair of guide rods and arranged parallel to the longitudinal axis,                    which round files are held in the first and the second head part without play in the longitudinal direction and transverse thereto, but exchangeably in round file receivers,                        with two mutually parallel file faces on one flat file, which is held without play in the longitudinal direction and transverse thereto, but exchangeably in flat file receivers,        wherein the pairs of guide rods and the respectively associated round files and the file faces are rotationally symmetrically arranged with respect to the longitudinal axis.        
It is achieved by the measures according to the invention that the cutting device only has to be rotated about its longitudinal axis if a change is to be made from one type of cutting tooth to the other cutting tooth. The two file faces for filing the two different types of depth limiters have different file directions.
The configuration according to FIG. 2 is particularly advantageous as all the files can be changed in a very simple manner according to wear. During the use of the sharpening device, on the other hand, a removal and reinsertion of the unworn files is not necessary.
Further advantages, features and details of the invention emerge from the following description of an embodiment with the aid of the drawings.